1. Field of the Invention
The present invention relates to a fuel cell cooling system, more specifically to a cooling system that performs cooling by absorbing heat by heat exchange, the heat being generated from power generation cells when a fuel cell generates power.
2. Description of Related Art
In a fuel cell system, when numerous power generation cells layered in the fuel cell generate power as hydrogen gas and oxygen gas react to each other, the power generation cells generate heat. Without heat dissipation, the power generation cells are overheated and unable to generate power. In order to cool the power generation cells when power is generated, a coolant cooling system is generally provided to the fuel cell. A cooling system is disclosed in Related Art 1 as a cooling system of the type. As shown in FIG. 7, a circulation pipe 12 is connected to a fuel cell 11 in the cooling system, the circulation pipe 12 circulating a coolant by a pump 13. A heat exchanger 14 is connected to the circulation pipe 12 on an upstream side of the pump 13. The heat exchanger 14 includes a radiator 15 and a fan 16, which blows air to the radiator 15.
LLC (long-life coolant), which contains ethylene glycol (antifreeze liquid) in water, is used as the coolant. When the pump 13 is driven to generate power, the coolant is supplied inside the fuel cell 11. Then, heat exchange occurs due to a temperature difference between heat generated from power generation cells and heat of the coolant, and thereby the power generation cells in the fuel cell 11 are cooled. In the process, the ethylene glycol contained in the coolant is thermolized, and thus a formic acid is produced, which then produces negative ions. Further, when the formic acid corrodes an internal surface of a circulation path of the coolant, positive ions are also produced. Thereby, the coolant includes impurity ions, which are a mixture of negative and positive ions. Since the ions are charged, the higher the concentration of the impurity ions is in the coolant, the higher the electric conductivity of the coolant is. Electricity generated by the fuel cell 11 thus leaks outside through the coolant as a medium.
In order to address the above described problems, a bypass pipe 17 is connected to the circulation pipe 12 in parallel with the pump 13 in Related Art 1. An ion exchanger 18 is connected to the bypass pipe 17, the ion exchanger 18 adsorbing and removing the impurity ions from the coolant. The ion exchanger 18 includes therein particulate anion exchange resins and particulate cation exchange resins as ion-exchange resins, the anion exchange resins adsorbing negative ions, the cation exchange resins adsorbing positive ions. The ion-exchange resins adsorb and remove the impurity ions, and thereby keeps the electric conductivity of the coolant from increasing.    [Related Art 1] Japanese Patent Laid-open Publication No. 2005-161117
However, the conventional cooling system described above has problems. Specifically, the coolant is used for cooling the power generation cells of the fuel cell 11, and thus heated due to heat exchange. Since the high-temperature coolant enters the ion exchanger 18, the ion-exchange resins are abnormally heated. It is thus required to use ion-exchange resins having a high heat resistant temperature. In addition, since it is required to take into account the heat resistant temperature of the ion-exchange resins, an operating temperature of the cooling system cannot be set high. Consequently, an allowable temperature range of the cooling system cannot be increased, and a selection range of the ion-exchange resins is limited. Further, the ion-exchange resins have problems not only of decline in the ion-exchange function, but also of heat degradation.